An online advertisement impression generally refers to the slot or space on the pages of a website that are available for displaying a single view of an advertisement along with its content. An advertisement event generally refers to active or passive actions that users take in response to an advertisement impression such as clicking an image, expanding an advertisement, or watching a video. Advertisers typically purchase advertisement impressions through bulk contracts directly with publishers. More recently, individual and targeted impressions have become available through real-time bidding (RTB) exchanges such as AdX, Admeld, Pubmatic, Rubicon, etc.
RTB advertising companies are contracted to deliver targeted quantities of advertisements over a period of time. For example, a contract may specify that 3,000,000 advertisements are to be displayed over a 30 day period. Alternatively, the contract may specify some number of events such as 100,000 clicks on the advertisement impressions over the period of time. In a simple scenario, these advertisement impressions are distributed evenly over the 30 day period resulting in a target of 100,000 impressions of that advertisement campaign each day. While many RTB exchanges can meet that requirement, there are other constraints, for example, expandable advertisements are not supported on all web sites or the site may not allow video advertisements longer than 15 seconds. Advertisers may want their advertisement to be displayed on the banner at the top of the page or supply only a few sizes of advertisements, thus limiting the inventory flexibility. Advertisers may also want to protect their brand by restricting the sites where the advertisements are shown. With these restrictions, RTB advertisers examine a vast number of potential impressions to find opportunities to deliver the advertisements.
Once an opportunity is located, an auction takes place with no guarantee that the ad will be purchased. There is no guarantee that similar opportunities will be offered in the future. The selected web sites could become unavailable, layout changes could alter the ad sizes supported, or another company could purchase the available inventory on a domain; therefore, impressions should be located and purchased when available. To handle large advertising campaigns in this uncertain environment, RTB advertisers integrate with multiple RTB exchanges, each of which may host auctions in multiple locations. This results in a continuous stream of impression opportunities at a rate of tens or hundreds of thousands per second. To deal with this flood of bidding opportunities, a geographically distributed set of servers is required to meet the time and scale requirements as described below.
Typical RTB exchanges conduct many thousands of auctions per second. Each auction is a candidate for multiple advertising campaigns. The bidder must determine which campaign, if any, is the best match for the auction. For organizations examining a large fraction of the bid opportunities for multiple advertising campaigns, the workload is beyond the capacity of a single server; therefore, a collection of machines is required to evaluate and respond to the volume of bid opportunities. A RTB control system is required to intelligently manage collections of advertisement servers.
RTB auctions require a response within 50-100 milliseconds for a bid to be considered; otherwise, the response is discarded. The time is measured from the exchange's location; therefore, latency is subtracted from the available analysis time. To reduce the intrinsic latency issues, bidders are placed physically close to the exchanges. Since exchanges are located around the world, bidders must be distributed around the world. A RTB control system has to manage bidders that are widely distributed geographically.
For many campaigns, advertisers need to use multiple publishers to reach campaign delivery goals, such as the number of impressions, to deliver within targeting criteria. For example, an advertiser may seek to deliver 100,000 impressions per day to women aged 30 to 45. Since each publisher markets its available impressions through a subset of the RTB exchanges, advertisers are required to integrate with multiple exchanges to deliver each campaign. The RTB control system is required to exercise consolidated campaign delivery control across multiple exchanges.